The expansion adds a new continent named Broken Isles. It's never been playable in World of Warcraft before, but was referenced in Warcraft 3.

What's more, Legion raises World of Warcraft's level cap to 110 and introduces a new class called Demon Hunter (see below for more details on the new character). There are also new dungeons and raids to explore, as well as new artifact weapons and an Honor System.

The new Demon Hunter
Blizzard

Here's a quick rundown of the key points for Legion, as provided by Blizzard:

The Demon Hunter (no connection to the band of the same name) sounds totally badass. The character can double-jump, and, its creepy-looking wings let it perform gliding attacks to surprise from above. In addition, Demon Hunters are blind, so they rely on "magically augmented sight" to see.

"Dominate your foes as a Demon Hunter, an elven outcast shunned for daring to wield the terrible powers of the Legion," Blizzard said. "Exhibiting superior mobility and a preternatural sense of awareness, Demon Hunters can tap into forbidden powers at times of dire need, metamorphosing into terrifying fel forms. Focus on Havoc to demolish any who stand in your way with fiery demonic attacks, or specialize in Vengeance and go toe to toe with even the most powerful demons, withstanding massive punishment as their attacks fuel your hatred."

"Twisted satyrs, savage drogbar, and cursed Kvaldir prowl the Isles alongside the Legion's marauding army," Blizzard said. "To overcome these threats, you will claim an Order Hall unique to your character class and lead your followers on a hunt for the Pillars of Creation--the secret to Azeroth's salvation."